In the past, projecting images onto a projection screen or other surface for viewing by a large number of people simultaneously, such as with transparencies and an overhead projector, provided a method for disseminating information in an efficient manner. However, because such transparencies were a fixed media, the user making the presentation was extremely limited in changing the form of the presentation except by using a large number of additional transparencies.
The ability of a user to change the form of a given presentation has been expanded significantly. In this regard, with the advancements in liquid crystal technology fixed media transparencies have evolved into dynamic images which are produced under the control of a computer or other video signal producing device. Thus, liquid crystal display panels have replaced the fixed transparencies to permit images, such as computer generated or video images, to be projected onto a screen or other surface for viewing purposes.
The capability of the presentation was expanded again when the user was given the ability to enter information interactively into the system in order to modify images, or generate additional images during the presentation, by simply directing a user controlled auxiliary beam of light onto specific areas of the projected image. In this manner, the user could interact with the computer or other device generating the projected image, in a manner similar to using a computer mouse control.
One such successful optical auxiliary input system is described in greater detail in the above-mentioned U.S. patent application Ser. No. 07/901,253. The optical auxiliary input system described therein includes an arrangement wherein a user directs a high intensity light from a light generating device, such as a flashlight or a laser pointer, onto a relatively lower intensity projected image on a viewing area, such as a screen to provide auxiliary information for the system.
The system includes a video information source, such as a computer, and a display projection arrangement, such as an overhead projector, for projecting images of the video information onto the viewing surface. An image processing arrangement, including an optical sensing device, detects and processes the displayed image reflecting from the viewing surface. Such a system detects the high intensity light images produced by the hand-held light generating device, and discriminates the high intensity light images from background ambient light and light produced by the video information source. In this manner, light signals from the hand-held light generating device can be detected on the viewing surface, and then used by the system for modifying subsequently the projected video information.
The optical input light directed onto the viewing surface is detected by determining that the light intensity reflecting from the viewing surface has exceeded a predetermined reference level. In this regard, the high intensity auxiliary light source produces a brighter intensity light than the intensity of the projected image. While such a technique is satisfactory for most applications, under certain conditions, the high intensity input light shining on the viewing surface can go undetected. In this regard, if the input light is directed onto a portion of the projected image which is of a low intensity, the total light being reflected from the viewing surface will not exceed the predetermined reference, and thus the input light will not be detected. Thus, it would be highly desirable to have an even more precise and accurate detection technique for discriminating the auxiliary input signal from the projected image and the ambient light.
In order to function properly, such an auxiliary optical input system includes an optical sensing device, in the form of a video camera, associated with the image processing arrangement which must be properly aligned with the projected image. In this regard, the image must be completely within the area sensed by the optical sensing device.
In one successful arrangement disclosed in the foregoing U.S. patent application Ser. No. 07/955,831, the optical sensing device was aligned by projecting a bright image from the projection arrangement onto the viewing surface. Sensing and indicating arrangements then determined whether or not the optical sensing device was properly aligned. Proper alignment required that light-to-dark transitions at the borders of the projected image would be as sharp as possible. The sensing and indicating devices would then indicate to the user to adjust the orientation of the optical sensing device until properly aligned. While such an alignment technique has proven to be highly successful, it would be desirable to have a new and improved technique which would be even easier for the user to quickly and easily align the sensing device, such as the video camera, with the projected image on the viewing surface. In this regard, it would be highly desirable to have a technique whereby the user can align the sensing device in a manner of seconds, with little or no effort.